Thermoplastic polyesters with improved shock-proof properties and impact modifying composition

ABSTRACT

The invention concerns thermoplastic polyesters (such as PET or PBT) comprising, by weight, the total being 100%: 60 to 99% of thermoplastic polyester; 1 to 40% of impact modifier comprising: (a) a core-shell copolymer (A), (b) an ethylene copolymer (B) selected among ethylene copolymers (B1) and an unsaturated carboxylic acid anhydride, ethylene copolymers (B2) and an unsaturated epoxy compound and mixtures thereof, (c) a copolymer (C) selected among ethylene copolymers (C1) and an alkyl (meth)acrylate, ethylene copolymers (C2) and (meth)acrylic acid optionally neutralised and mixtures thereof. The invention also concerns an impact modifying composition which can be added in thermoplastic polyesters to improve their shock-proof properties and comprising constituents (A), (B) and (C).

FIELD OF THE INVENTION

The present invention relates to thermoplastic polyesters havingimproved impact properties and to impact-modifier compositions.

BACKGROUND OF THE INVENTION

Thermoplastic polyesters, such as PBT (polybutylene terephthalate) andPET (polyethylene terephthalate) possess excellentdimensional-stability, heat-resistance and chemical-resistanceproperties which are used in the electrical, electronic andmotor-vehicle fields. However, at high temperature, during conversionoperations, a reduction in the molecular weight of the polymer mayoccur, leading to a reduction in the impact strength properties. Inaddition, polyesters have poor fracture-resistance properties in thecase of notched components.

The present invention provides thermoplastic polymers in which animpact-modifier composition is added in order to obtain improved impactproperties, including low-temperature toughness. The present inventionalso relates to this impact-modifier composition that is added to thepolyesters to improve the impact properties thereof. These modifiercompositions make it possible to achieve impact properties superior tothose obtained with each of the compounds separately.

Patent U.S. Pat. No. 4,753,890 (=EP 174,343) describes polyesters, suchas polyethylene terephthalate (PET) or polybutylene terephthalate (PBT)modified by ethylene-alkyl (meth)acrylate-glycidyl (meth)acrylatecopolymers.

Patent EP 737,715 describes PBTs modified by a blend of anethylene-methyl methacrylate-glycidyl methacrylate copolymer and of acopolymer of the core-shell type. These core-shell copolymers comprisefine particles having an elastomer core and a thermoplastic shell.

Patent EP 531,008 describes PBT/polycarbonate blends containingcopolymer core-shells and copolymers which are either ethylene-glycidylmethacrylate copolymers or ethylene-vinyl acetate-glycidyl methacrylatecopolymers.

Patent U.S. Pat. No. 5,369,154 describes PET/polycarbonate blendscontaining four different modifiers: a copolymer comprising an epoxide,a copolymer core-shell, an SBR- or SBS- or EPR-type elastomer and anSAN- or ABS-type copolymer.

Patent EP 115,015 describes PET or PBT containing linear low-densitypolyethylene (LLDPE), glass fibres and optionally a core-shellcopolymer.

Patent EP 133,993 describes PET containing a core-shell copolymer and acopolymer of ethylene with either an alkyl acrylate or (meth)acrylicacid.

Japanese Patent Application JP 01,247,454 A, published on 3 Oct. 1989describes PBT containing an ethylene-alkyl (meth)acrylate copolymer andan ethylene-glycidyl methacrylate copolymer.

Patents EP 838,501 and EP 511,475 describe compositions similar to thoseof the above Japanese application.

Patent EP 803,537 describes PET and polycarbonate containing a copolymercomprising glycidyl methacrylate. Firstly, the polycarbonate and thecopolymer comprising glycidyl methacrylate are blended together and thenthis blend is incorporated into the PET.

Patent EP 187,650 describes PET containing a core-shell copolymer and acopolymer of ethylene with either maleic anhydride or a (meth)acrylicacid.

It has been seen from the prior art that saturated polyesters can havetheir impact properties improved by the addition of a core-shellcopolymer. These polymers have a particularly well defined structure inwhich the core consists of a polymer having an elastomeric character andin which the shell has a thermoplastic character. It has also been seenthat the improvement in impact strength may be obtained by alsoincorporating a dispersed phase of an impact modifier optionallycontaining reactive functional groups capable of reacting with thefunctional groups of the polyesters. This reactivity makes it possibleto ensure a fine and homogeneous dispersion of the modifier as well asgood adhesion. The core-shell copolymer may itself also befunctionalized in order to allow better adhesion to the matrix. However,this reactivity is sometimes high and may lead to a reduction in themelt flow index. This reduction in the melt flow index is prejudicial tothe injection moulding of large parts or of fine parts.

It has now been found that it is possible to improve the impactproperties of thermoplastic polyesters by adding to them three kinds ofmodifier, namely: (a) a core-shell copolymer, (b) anethylene-unsaturated epoxide copolymer or an ethylene-unsaturatedcarboxylic acid anhydride copolymer or blends thereof and (c) anethylene-alkyl (meth)acrylate copolymer or an optionally neutralizedethylene-(meth)acrylic acid copolymer or blends thereof. Thismodification does not result in a drop in the melt flow index comparedwith the prior art and even improves it. These modifiers improve theimpact strength properties either at room temperature or at lowtemperatures, depending on the ratio which is chosen between the threecomponents (a), (b) and (c), compared with compositions encountered inpatents EP 511,475 and EP 174,343. They also allow the material to havebetter melt flow compared with compositions as described in EP 737,715.

The present invention relates to thermoplastic polyester compositionscomprising, by weight, the total being 100%:

-   -   60 to 99% of a thermoplastic polyester;    -   1 to 40% of an impact modifier comprising:        -   (a) a core-shell copolymer (A);        -   (b) an ethylene copolymer (B) chosen from            ethylene-unsaturated carboxylic acid anhydride copolymers            (B1), ethylene-unsaturated epoxide copolymers (B2) and            blends thereof;        -   (c) a copolymer (C) chosen from ethylene-alkyl            (meth)acrylate copolymers (C1), optionally neutralized            ethylene-(meth)acrylic acid copolymers (C2) and blends            thereof.

The present invention also relates to an impact-modifier compositionwhich can be added to thermoplastic polyesters to improve their impactproperties and which comprise:

-   -   (a) a core-shell copolymer (A);    -   (b) an ethylene copolymer (B) chosen from ethylene-unsaturated        carboxylic acid anhydride copolymers (B1), ethylene-unsaturated        epoxide copolymers (B2) and blends thereof;    -   (c) a copolymer (C) chosen from ethylene-alkyl (meth)acrylate        copolymers (C1), optionally neutralized ethylene-(meth)acrylic        acid copolymers (C2) and blends thereof.

DESCRIPTION OF THE INVENTION

The term “MFI” (standing for Melt Flow Index) denotes the melt flowindex in g/10 minutes at a given temperature and under a given load.

The term “thermoplastic polyester” denotes polymers which are saturatedproducts coming from the condensation of glycols and of dicarboxylicacids, or of their derivatives. Preferably, they comprise the productsof the condensation of aromatic dicarboxylic acids having from 8 to 14carbon atoms and of at least one glycol chosen from the group consistingof neopentyl glycol, cyclohexanedimethanol and aliphatic glycols offormula HO(CH₂)_(n)OH in which n is an integer ranging from 2 to 10. Upto 50 mol % of the aromatic dicarboxylic acid may be replaced with atleast one other aromatic dicarboxylic acid having from 8 to 14 carbonatoms, and/or up to 20 mol % may be replaced with an aliphaticdicarboxylic acid having from 2 to 12 carbon atoms.

The preferred polyesters are polyethylene terephthalate (PET),poly(1,4-butylene) terephthalate (PBT), 1,4-cyclohexylene dimethyleneterephthalate/isophthalate) and other esters derived from aromaticdicarboxylic acids such as isophthalic acid, dibenzoic acid, naphthalenedicarboxylic acid, 4,4′-diphenylenedicarboxylic acid,bis(p-carboxyphenyl)methane acid, ethylene bis(p-benzoic) acid,1,4-tetramethylene bis(p-oxybenzoic) acid, ethylene bis(para-oxybenzoic)acid, 1,3-trimethylene bis(p-oxybenzoic) acid, and glycols such asethylene glycol, 1,3-trimethylene glycol, 1,4-tetramethylene glycol,1,6-hexamethylene glycol, 1,3-propylene glycol, 1,8-octamethylene glycoland 1,10-decamethylene glycol.

The MFI of these polyesters, measured at 250° C. and with 2.16 kg or 5kg (for PBT) or at 275° C. and with 2.16 kg (for PET), may vary from 2to 100 and advantageously from 10 to 80.

It would not be outside the scope of the invention if the polyestersconsisted of several diacids and/or several diols. It is also possibleto use a blend of various polyesters.

It would not be outside the scope of the invention if the polyesterscontained copolyetheresters. These copolyetheresters are copolymerscontaining polyester blocks and polyether blocks having polyether unitsderived from polyetherdiols such as polyethylene glycol (PEG),polypropylene glycol (PPG) or polytetramethylene glycol (PTMG),dicarboxylic acid units such as terephthalic acid units, and short,chain-extender, diol units such as glycol (1,2-ethanediol) or1,4-butanediol. The linking of the polyethers with the diacids forms theflexible segments whereas the linking of the glycol or butanediol withthe diacids forms the rigid segments of the copolyetherester. Thesecopolyetheresters are thermoplastic elastomers. The proportion of thesecopolyetheresters may represent from 0 to 500 parts per 100 parts ofthermoplastic polyester.

It would not be outside the scope of the invention if the polyesterscontained polycarbonate. In general, the term “polycarbonate” denotespolymers comprising the following units:

in which R₁ is an aliphatic, alicyclic or aromatic divalent group whichmay contain up to 8 carbon atoms. By way of example of R₁, mention maybe made of ethylene, propylene, trimethylene, tetramethylene,hexamethylene, dodecamethylene, poly(1,4-[2-butenylene]),poly(1,10-[(2-ethyldecylene]), 1,3-cyclopentylene, 1,3-cyclohexylene,1,4-cyclohexylene, m-phenylene, p-phenylene, 4,4′-diphenylene,2,2-bis(4-phenylene)propane and benzene-1,4-dimethylene. Advantageously,at least 60% of the R₁ groups in the polycarbonate and preferably allthe groups R₁ are aromatic groups of formula:—R—Y—R₃—in which R₂ et R₃ are divalent monocyclic aromatic radicals and Y is alinking radical containing one or two atoms which separate R₂ and R₃.The free valences are generally in the meta or para position withrespect to Y. R₂ and R₃ may be substituted or unsubstituted phenylenes;as substituents, mention may be made of alkyl, alkenyl, halogen, nitroand alkoxy. Preferably, the phenylenes are unsubstituted; they may betogether or separately meta or para and are preferably para. The linkingradical Y is preferably such that one atom separates R₂ from R₃ and ispreferably a hydrocarbon radical such as methylene, cyclohexylmethylene,2-[2.2.1]bicycloheptylmethylene, ethylene, 2,2-propylene,1,1-(2,2-dimethylpropylene), 1,1-cyclohexylene, 1,1-cyclopentadecylene,cyclo-dodecylene, carbonyl, the oxy radical, the thio radical andsulfone. Preferably, R₁ is 2,2-bis(4-phenylene)propane which comes frombisphenol A, that is to say Y is isopropylidene and R₂ and R₃ are eachp-phenylene. Advantageously, the intrinsic viscosity of thepolycarbonate, measured in methylene chloride at 25° C., is between 0.3and 1 dl/g.

The proportion of polycarbonate may represent from 0 to 300 parts per100 parts of thermoplastic polyester.

With regard to the core-shell copolymer (A), abbreviated as CS in whatfollows, this is in the form of fine particles having an elastomer coreand at least one thermoplastic shell. The particle size is generallybetween 50 and 1000 nm and advantageously between 100 and 500 nm.

By way of example of the core, mention may be made of isoprenehomopolymers or butadiene homopolymers, copolymers of isoprene with atmost 30 mol % of a vinyl monomer and copolymers of butadiene with atmost 30 mol % of a vinyl monomer. The vinyl monomer may be styrene, analkylstyrene, acrylonitrile or an alkyl (meth)acrylate. Another corefamily consists of the homopolymers of an alkyl (meth)acrylate and thecopolymers of an alkyl (meth)acrylate with at most 30 mol % of a vinylmonomer. The alkyl (meth)acrylate is advantageously butyl acrylate. Thevinyl monomer may be styrene, an alkylstyrene, acrylonitrile, butadieneor isoprene. The core of the copolymer (A) may be completely or partlycrosslinked. All that is required is to add at least difunctionalmonomers during the preparation of the core; these monomers may bechosen from poly(meth)acrylic esters of polyols, such as butylenedi(meth)acrylate and trimethylolpropane trimethacrylate. Otherdifunctional monomers are, for example, divinylbenzene, trivinylbenzene,vinyl acrylate and vinyl methacrylate. The core can also be crosslinkedby introducing into it, by grafting or as a comonomer during thepolymerization, unsaturated functional monomers such as anhydrides ofunsaturated carboxylic acids, unsaturated carboxylic acids andunsaturated epoxides. Mention may be made, for example, of maleicanhydride, (meth)acrylic acid and glycidyl methacrylate.

The shell(s) are styrene homopolymers, alkylstyrene homopolymers ormethyl methacrylate homopolymers, or copolymers comprising at least 70mol % of one of the above monomers and at least one comonomer chosenfrom the other above monomers, vinyl acetate and acrylonitrile. Theshell may be functionalized by introducing into it, by grafting or as acomonomer during the polymerization, unsaturated functional monomerssuch as anhydrides of unsaturated carboxylic acids, unsaturatedcarboxylic acids and unsaturated epoxides. Mention may be made, forexample, of maleic anhydride, (meth)acrylic acid and glycidylmethacrylate.

By way of example, mention may be made of core-shell copolymers (A)having a polystyrene shell and core-shell copolymers (A) having a PMMAshell. There are also core-shell copolymers (A) having two shells, onemade of polystyrene and the other, on the outside, made of PMMA.Examples of copolymers (A) and their method of preparation are describedin the following patents: U.S. Pat. No. 4,180,494, U.S. Pat. No.3,808,180, U.S. Pat. No. 4,096,202, U.S. Pat. No. 4,260,693, U.S. Pat.No. 3,287,443, U.S. Pat. No. 3,657,391, U.S. Pat. No. 4,299,928 and U.S.Pat. No. 3,985,704.

By way of example, mention may be made of core-shell copolymers (A)having a core based on an alkyl acrylate or on a polyorganosiloxanerubber or a mixture thereof and a shell based on a polyalkylmethacrylate or a styrene-acrylonitrile copolymer, characterized in thatthe said impact additive comprises:

-   a) 70 to 90% by weight of an elastomeric crosslinked core which is    composed:    -   1) of 20 to 100% by weight, and preferably 20 to 90%, of a core        consisting of an n-alkyl acrylate copolymer (I), the alkyl group        of which has a number of carbons ranging from 5 to 12 or a        mixture of an alkyl acrylate, the linear or branched alkyl group        of which has a number of carbons ranging from 2 to 12, or of a        polyorganosiloxane rubber, of a polyfunctional crosslinking        agent possessing in its molecule unsaturated groups, at least        one of which is of the CH₂═C<vinyl type, and, optionally, of a        polyfunctional grafting agent possessing in its molecule        unsaturated groups, at least one of which is of the CH₂═CH—CH₂—        allyl type, the said core containing a molar quantity of        crosslinking agent and, optionally, of a grafting agent ranging        from 0.05 to 5%,    -   2) of 80 to 0% by weight, and preferably 80 to 10% of a sheath        surrounding the core and consisting of an n-alkyl acrylate        copolymer (II), the alkyl group of which has a number of carbons        ranging from 4 to 12 or of a mixture of alkyl acrylates as        defined above in 1) and of a grafting agent possessing in its        molecule unsaturated groups, at least one of which is of the        CH₂═CH—CH₂— allyl type, the said sheath containing a molar        amount of grafting agent ranging from 0.05 to 2.5%;-   b) 30 to 10% by weight of a shell grafted onto the said core    consisting of a polymer of an alkyl methacrylate, the alkyl group of    which has a number of carbons ranging from 1 to 4 or else of a    random copolymer of an alkyl methacrylate, the alkyl group of which    has a number of carbons ranging from 1 to 4 and of an alkyl    acrylate, the alkyl group of which has a number of carbons ranging    from 1 to 8, containing a molar amount of alkyl acrylate ranging    from 5 to 40% or else consisting of a styrene-acrylonitrile    copolymer.    Optionally, 0.1 to 50% by weight of the vinyl monomers possess    functional groups.    This type of core-shell copolymer is described in the Applicant's    Patent Application EP-A-776 915 and Patent U.S. Pat. No. 5,773,520.

By way of example, mention may be made of core-shell copolymers (A)consisting (i) of 75 to 80 parts of a core comprising at least 93 mol %of butadiene, 5 mol % of styrene and 0.5 to 1 mol % of divinylbenzeneand (ii) of 25 to 20 parts of two shells essentially of the same weight,the inner one made of polystyrene and the outer one made of PMMA.

Advantageously, the core represents 70 to 90% by weight of (A) and theshell represents 30 to 10%.

With regard to ethylene-unsaturated carboxylic acid anhydride copolymers(B1), these may be polyethylenes grafted by an unsaturated carboxylicacid anhydride or ethylene-unsaturated carboxylic acid anhydridecopolymers which are obtained, for example, by radical polymerization.

The unsaturated carboxylic acid anhydride may be chosen, for example,from maleic, itaconic, citraconic, allylsuccinic,cyclohex-4-ene-1,2-dicarboxylic,4-methylenecyclohex-4-ene-1,2-dicarboxylic,bicyclo-[2.2.11]hept-5-ene-2,3-dicarboxylic andx-methylbicyclo-[2.2.11]hept-5-ene-2,2-dicarboxylic anhydrides.Advantageously, maleic anhydride is used. It would not be outside thescope of the invention to replace all or part of the anhydride with anunsaturated carboxylic acid such as, for example, (meth)acrylic acid.

With regard to the polyethylenes onto which the unsaturated carboxylicacid anhydride is grafted, the term “polyethylene” should be understoodto mean homopolymers or copolymers.

By way of comonomers, mention may be made of:

-   -   alpha-olefins, advantageously those having from 3 to 30 carbon        atoms; by way of examples of alpha-olefins, mention may be made        of propylene, 1-butene, 1-pentene, 3-methyl-1-butene, 1-hexene,        4-methyl-1-pentene, 3-methyl-1-pentene, 1-octene, 1-decene,        1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene,        1-eicocene, 1-dococene, 1-tetracocene, 1-hexacocene,        1-octacocene and 1-triacontene; these alpha-olefins may be used        separately or as a mixture of two or more of them;    -   esters of unsaturated carboxylic acids, such as, for example,        alkyl (meth)acrylates, the alkyls possibly having up to 24        carbon atoms; examples of alkyl acrylates or methacrylates are        especially methyl methacrylate, ethyl acrylate, n-butyl        acrylate, isobutyl acrylate and 2-ethylhexyl acrylate;    -   vinyl esters of saturated carboxylic acids, such as, for        example, vinyl acetate or vinyl propionate;    -   dienes such as, for example, 1,4-hexadiene.    -   the polyethylene may include several of the above comonomers.        Advantageously, the polyethylene, which may be a blend of        several polymers, comprises at least 50 mol % and preferably 75        mol % of ethylene and its density may be between 0.86 and 0.98        g/cm³. The MFI (at 190° C./2.16 kg) is advantageously between        0.1 and 1000.        By way of example of polyethylenes, mention may be made of:    -   low-density polyethylene (LDPE)    -   high-density polyethylene (HDPE)    -   linear low-density polyethylene (LLDPE)    -   very low-density polyethylene (VLDPE)    -   polyethylene obtained by metallocene catalysis, that is to say        polymers obtained by the copolymerization of ethylene and of an        alpha-olefin such as propylene, butene, hexene or octene in the        presence of a single-site catalyst generally consisting of a        zirconium or titanium atom and of two alkyl cyclic molecules        linked to the metal. More specifically, the metallocene        catalysts are usually composed of two cyclopentadiene rings        linked to the metal. These catalysts are frequently used with        aluminoxanes as cocatalysts or activators, preferably        methylaluminoxane (MAO). Hafnium may also be used as the metal        to which the cyclopentadiene is fixed. Other metallocenes may        include transition metals of Groups IV A, V A and VI A. Metals        from the series of lanthanides may also be used.    -   EPR (ethylene-propylene-rubber) elastomers;    -   EPDM (ethylene-propylene-diene) elastomers;    -   blends of polyethylene with an EPR or an EPDM;    -   ethylene-alkyl (meth)acrylate copolymers possibly containing up        to 60%, and preferably 2 to 40%, by weight of (meth)acrylate.        The grafting is an operation known per se.

With regard to the ethylene-unsaturated carboxylic acid anhydridecopolymers, that is to say those in which the unsaturated carboxylicacid anhydride is not grafted, these are copolymers of ethylene, theunsaturated carboxylic acid anhydride and, optionally another monomerwhich may be chosen from the comonomers mentioned above in the case ofthe ethylene copolymers intended to be grafted.

Advantageously, ethylene-maleic anhydride copolymers and ethylene-alkyl(meth)acrylate-maleic anhydride copolymers are used. These copolymerscomprise from 0.2 to 10% by weight of maleic anhydride and from 0 to40%, preferably 5 to 40%, by weight of alkyl (meth)acrylate. Their MFIs(190° C./2.16 kg) are between 0.5 and 200. The alkyl (meth)acrylateshave already been described above. It is possible to use a blend ofseveral copolymers (B1). It is also possible to use an ethylene-maleicanhydride copolymer/ethylene-alkyl (meth)acrylate-maleic anhydridecopolymer blend.

The copolymer (B1) is commercially available—produced by radicalpolymerization at a pressure which may range between 200 and 2500 barand is sold in the form of granules.

With regard to (B2), the ethylene-unsaturated epoxide copolymers may beobtained by the copolymerization of ethylene with an unsaturated epoxideor by grafting the unsaturated epoxide to the polyethylene. The graftingmay be carried out in the solvent phase or onto the polyethylene in themelt in the presence of a peroxide. These grafting techniques are knownper se. With regard to the copolymerization of ethylene with anunsaturated epoxide, it is possible to use so-called radicalpolymerization processes usually operating at pressures between 200 et2500 bar. By way of example of unsaturated epoxides, mention may be madeof:

-   -   aliphatic glycidyl esters and ethers, such as allyl glycidyl        ether, vinyl glycidyl ether, glycidyl maleate, glycidyl        itaconate, glycidyl acrylate and glycidyl methacrylate; and    -   alicyclic glycidyl esters and ethers, such as 2-cyclohex-1-ene        glycidyl ether, diglycidyl cyclohexene-4-5-carboxylate, glycidyl        cyclohexene-4-carboxylate, glycidyl        2-methyl-5-norbornene-2-carboxylate and diglycidyl        endo-cis-bicyclo[2.2.1]hept-5-ene-2,3-dicarboxylate.        With regard to grafting, the copolymer is obtained by grafting a        polyethylene homopolymer or copolymer as described in the case        of (B1) above, except that an epoxide is grafted instead of an        anhydride.        With regard to copolymerization, the principle is similar to        that described in the case of (B1) above except that an epoxide        is used. There may also be other comonomers, as in the case of        (B1).

The product (B2) is advantageously an ethylene-alkyl(meth)acrylate-unsaturated epoxide copolymer or an ethylene-unsaturatedepoxide copolymer. Advantageously, it may contain up to 40%, preferably5 to 40%, by weight of alkyl (meth)acrylate and up to 10%, preferably0.1 to 8%, by weight of unsaturated epoxide.

Advantageously, the epoxide is glycidyl (meth)acrylate.

Advantageously, the alkyl (meth)acrylate is chosen from methyl(meth)acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate and2-ethylhexyl acrylate. The amount of alkyl (meth)acrylate isadvantageously from 20 to 35%. The MFI (at 190° C./2.16 kg) isadvantageously between 0.5 and 200.

It is possible to use a blend of several copolymers (B2). It is alsopossible to use an ethylene-alkyl (meth)acrylate-unsaturated epoxidecopolymer/ethylene-unsaturated epoxide copolymer blend.

This copolymer (B2) may be obtained by the radical polymerization of themonomers.

It is also possible to use a blend of copolymers (B1) and (B2).

With regard to the ethylene-alkyl (meth)acrylate copolymer (C1), thealkyls may have up to 24 carbon atoms. Examples of alkyl acrylates ormethacrylates are especially methyl methacrylate, ethyl acrylate,n-butyl acrylate, isobutyl acrylate and 2-ethylhexyl acrylate. The MFI(at 190° C./2.16 kg) of these copolymers is advantageously between 0.1and 50. The alkyl (meth)acrylate content may be up to 40% by weight of(C1). Advantageously, the (meth)acrylate content is between 5 and 35% byweight of (C1). These copolymers may be manufactured by radicalpolymerization in a tube or autoclave at pressures of between 300 and2500 bar.

With regard to the ethylene-(meth)acrylic acid copolymers (C2), the(meth)acrylic acid content may be up to 10 mol %, and advantageouslybetween 1 and 5 mol %, of (C2). It would not be outside the scope of theinvention if (C2) were to contain an alkyl (meth)acrylate in aproportion possibly up to 40% by weight of (C2). The acid functions maybe completely or partly neutralized by a cation, such as lithium,sodium, potassium, magnesium, calcium, strontium, zinc and cadmium. TheMFI (at 190° C./2.16 kg) of these copolymers is advantageously between0.1 and 50. These copolymers may be manufactured by radicalpolymerization in a tube or autoclave at pressures of between 300 and2500 bar.

It is also possible to use a blend of copolymers (C1) and (C2).

Advantageously, the impact constituents are in the following proportionsby weight for a total of 100%:

-   (A) 15 to 80%-   (B) 5 to 60%-   (C) 5 to 80%

Particularly useful proportions are the following: A 20 to 35 25 to 3540 to 75 B 40 to 60  5 to 10 10 to 35 C 10 to 40 60 to 70 10 to 35 A +B + C 100 100 100Advantageously, the thermoplastic polyester compositions of theinvention comprise, per 100 parts by weight, 65 to 95 parts and 35 to 5parts of polyester and of impact modifier, respectively.

The invention also relates to an impact-modifier composition havingthese proportions.

The thermoplastic polyesters of the invention may also include, inaddition to the impact modifier, slip agents, heat stabilizers,antiblocking agents, antioxidants, UV stabilizers and fillers. Thefillers may be glass fibres, fire retardants, talc or chalk. Thesefillers may be contained in the impact modifiers.

The thermoplastic polyester/impact-modifier blends are prepared by theusual techniques for thermoplastic polymers in single-screw ortwin-screw extruders, mixers or apparatuses of the BUSS® Ko-kneadertype. The polyester and the constituents of the impact modifier, namelythe copolymers (A), (B) and (C), may be introduced separately into theblending device. The constituents of the impact modifier may also beadded in the form of a blend prepared in advance, possibly in the formof a masterbatch in the polyester. The additives may be added into theseapparatuses, such as the slip agents, the antiblocking agents, theantioxidants, the UV stabilizers and the fillers, whether as they are orin the form of a masterbatch in the polyester or else in the form of amasterbatch with one or more of the copolymers (A) to (C). Theimpact-modifier composition comprising (A) to (C) which may be added tothe polyesters is also prepared by the previous usual technique ofblending thermoplastic polymers.

EXAMPLES

All the examples were produced with compositions comprising, by weight,between 70 to 80% of polyester and between 30 to 20% of impact modifier.The impact modifier either consists of A, B and C, in the case of theexamples according to the invention, or of A and B, or of B and C, or ofA, or of B, or of C. The notched Charpy impact strength complies withthe ISO 179:93 standard (with kJ/m² as unit of measure) and the notchedIzod impact strength is measured according to the ASTM D256 standard(with pound-foot/inch as unit of measure)—the higher the measuredimpact-strength value the better the impact strength.

The examples below were produced with PBT or with PET as polyester.

-   -   The following examples were produced with compositions        comprising 80% by weight of PBT and 20% by weight of impact        modifier.        These examples were produced with the following products:

-   AX 8900: ethylene-methyl acrylate-glycidyl methacrylate (GMA)    copolymer comprising, by weight, 25% acrylate and 8% GMA, having an    MFI of 6 (190° C./2.16 kg). It is sold under the Atofina brand name    LOTADER®;

-   AX 8930: ethylene-methyl acrylate-glycidyl methacrylate (GMA)    copolymer comprising, by weight, 25% acrylate and 3% GMA, having an    MFI of 6 (190° C./2.16 kg). It is sold under the Atofina brand name    LOTADER®;

-   Lotryl: ethylene-2-ethylhexyl acrylate copolymer comprising 35%    acrylate by weight and having an MFI of 2 (190° C./2.16 kg);

-   E920: MBS-type core-shell copolymer with a core essentially based on    butadiene-styrene and a shell of PMMA, sold by Atofina under the    brand name METABLEND®;

-   EXL 2314: epoxy-functionalized acrylic core-shell copolymer sold by    Röhm and Haas under the brand name PARALOID®;

-   PBT: polybutylene terephthalate having an MFI of 20 (250° C./2.16    kg) sold by BASF under the brand name ULTRADUR® B4500.

DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the notched Charpy impact strength of PBT containing AX8900 (comparative example), PBT containing EXL 2314 (comparativeexample) and PBT containing simultaneously (according to the invention)AX 8900, Lotryl and a core-shell copolymer. The proportions by weight ofthe constituents of the impact modifier are in the following format:(2.8/11.2/6, AX8900/lotryl/core-shell) (example).

The impact strength values are indicated at four different temperaturesfor each composition. The values in FIG. 1 are also given in TABLE 1below.

TABLE 1 Notched Charpy impact strength (kJ/m²) T = T = T = T = Impactmodifier 23° C. 0° C. −20° C. −40° C. AX 8900 76.4 17 9 6.5 2.8/11.2/673 20.5 14.5 9.1 AX 8900/Lotryl/EXL 2314 2.8/11.2/6 57.2 18 14 11.3 AX8900/Lotryl/E920 1.4/12.6/6 63.7 10.4 AX 8900/Lotryl/EXL 2314 1.2/4.8/1481.7 10.1 AX 8900/Lotryl/EXL 2314 EXL 2314 61.5 15.4 9.8 7

FIG. 2 shows the MFI of the above compositions containing the variousimpact modifiers and, in addition, the MFI of the PBT without anymodifier: “pure PBT”. The values are also given in TABLE 2 below.

TABLE 2 MFI (250° C./2.16 kg) COMPOSITION 0.63 PBT + AX 8900 4.1 PBT +2.8/11.2/6 AX 8900/Lotryl/EXL 2314 6.5 PBT + 2.8/11.2/6 AX8900/Lotryl/E920 5.7 PBT + 1.4/12.6/6 AX 8900/Lotryl/EXL 2314 4.4 PBT +1.2/4.8/14 AX 8900/Lotryl/EXL 2314 7.4 PBT + EXL 2314 20 Pure PBT

It may be clearly seen that the modifier of the invention gives betterimpact, particularly cold impact, results than AX 8900 or EXL 2314.However, the MFI is lower than with EXL 2314 used alone and much higherthan with AX 8900 used alone, but easily sufficient for injectionmoulding.

FIG. 3 shows the notched Charpy impact strength at +23° C. for PBTcontaining, as impact modifier, either AX 8900, or Lotryl, or a mixtureof these impact modifiers. These compositions are not according to theinvention. FIG. 4 shows the impact strengths of the same compositionsfor other temperatures. The values are also given in TABLES 3 and 4.

TABLE 3 AX 8900/Lotryl Notched Charpy proportions impact strength AX8900 Lotryl (temperature 23° C.) 100 0 76.4 70 30 65.7 30 70 60.35 20 8053.9 10 90 15 0 100 5

TABLE 4 PBT + 20% Notched Charpy impact strength (AX 8900 + Lotryl) T =0° C. T = −20° C. T = −40° C. 100/0 AX 8900/Lotryl 17 9.1 6.2 70/30 AX8900/Lotryl 18.9 13.4 8.2 30/70 AX 8900/Lotryl 15.9 13.4 8.75 20/80 AX8900/Lotryl 14.6 12 8.2 10/90 AX 8900/Lotryl 7.5 0/100 AX 8900/Lotryl3.6

FIG. 5 shows the MFI of the above compositions containing the variousimpact modifiers and also the MFI of the PBT without a modifier: “purePBT”. The values are also given in TABLE 5 below.

TABLE 5 PBT + 20% MFI (AX 8900 + Lotryl) (250° C./2.16 kg) 100/0 AX8900/Lotryl 0.63 70/30 AX 8900/Lotryl 1.5 30/70 AX 8900/Lotryl 2.7 20/80AX 8900/Lotryl 3.6 10/90 AX 8900/Lotryl 5.5 0/100 AX 8900/Lotryl 12 PurePBT 20

Comparing FIG. 1 with FIG. 4, it may be seen that, with the modifier ofthe invention, a better impact strength is obtained, particularly at 0°C. and below 0° C., while still having a higher MFI.

FIG. 6 shows the notched Charpy impact strength at −40° C. for PBTcontaining, as impact modifier, either AX (AX8900 or AX8930), or acore-shell (EXL2314 or E920) or a mixture of these impactmodifiers—these compositions are not according to the invention.

FIG. 7 shows the impact strength of these same compositions at +23° C.In these FIGS. 6 and 7, the epoxide-based copolymer has been denoted byAX and the core-shell by CS. The values are also given in TABLE 6 andTABLE 7.

TABLE 6 PBT + 20% (AX + CS) AX = AX 8900 or Notched Charpy impactstrength at −40° C. AX 8930 AX 8900/ AX 8900/ AX 8930/ AX 8930/ CS = EXL2314 or E920 EXL 2314 E920 EXL 2314 E920 100/0 AX/CS 6.2 6.2 5 5 70/30AX/CS 9.8 10 8.8 9.9 30/70 AX/CS 7.8 14.75 7.1 9.8 20/80 AX/CS 9.2 10.2510/90 AX/CS 13.8 0/100 AX/CS 6.75 8.2 6.75 8.2

TABLE 7 PBT + 20% (AX + CS) AX = AX 8900 or Notched Charpy impactstrength at +23° C. AX 8930 AX 8900/ AX 8900/ AX 8930/ AX 8930/ CS = EXL2314 or E920 EXL 2314 E920 EXL 2314 E920 100/0 AX/CS 76.4 76.4 55.2 55.270/30 AX/CS 99 62.2 67.5 61 30/70 AX/CS 91.8 88.9 82.6 88.4 20/80 AX/CS87.6 79.5 10/90 AX/CS 80 0/100 AX/CS 62 18 62 18

FIG. 8 shows the MFI of the above compositions containing the variousimpact modifiers and also the MFI of the PBT without a modifier: “purePBT”. The values are also given in TABLE 8 below.

TABLE 8 PBT + 20% (AX + CS) AX = AX 8900 or AX 8930 MFI (250° C./2.16kg) CS = EXL 2314 or E920 no change with the type of AX and CS 100/0AX/CS 0.63 70/30 AX/CS 0.9 30/70 AX/CS 1.63 20/80 AX/CS 3.5 10/90 AX/CS3 0/100 AX/CS 7.4 Pure PBT 20

Comparing FIG. 1 with FIG. 6, it may be seen that the modifier of theinvention results in superior cold impact strength values. By examiningFIGS. 2, 5 and 8, it may be seen that the MFI of those compositions ofthe invention in which A, B and C are combined is unexpectedly higher incomparison with that obtained by combining the copolymers in pairs: Awith B or B with C.

-   -   The examples below were produced with PBT/impact modifier        compositions such as those defined in % by weight in TABLE 9.        This table also give other values, such as the MFI of the        compositions appearing therein, together with their impact        strength by measuring the notched Izod impact behaviour        according to the standard defined above at various temperatures        T (T 20° C., −20° C., −30° C. and −40° C.).        The compositions exemplified below were produced with the        following products:

-   PBT: polybutylene terephthalate having an MFI of 8.4 (250° C./5 kg)    sold under the brand name CELANEX®1600A by Ticona;

-   Lotryl: ethylene-butyl acrylate copolymer comprising 30% by weight    of acrylate and having an MFI of 2(190° C./2.16 kg);

-   AX8900: composition defined above;

-   AM939: core-shell with an n-octyl acrylate core and a methyl    methacrylate shell in proportions of 70 to 90% by weight for the    n-octyl acrylate and 10 to 30% for the methyl methacrylate.    In view of the values listed in TABLE 9, it may be clearly seen that    the compositions which include the impact modifier according to the    invention gives better impact strength results within an exemplified    temperature range going from room temperature to −40° C., unlike the    compositions comprising only AX8900 (comparative 1) or AM939    (comparative 2) as impact modifier.    Impact strength tests were also carried out with compositions not    according to the invention comprising two impact modifiers. These    are the compositions called comparatives 3, 5 and 6 in TABLE 9. When    the impact strength results obtained with such compositions are    compared with the results obtained with the compositions comprising    the trio AM939/Lotryl/AX8900, it is found that the use of the impact    modifier according to the invention gives very good impact strength    values over the temperature range exemplified, which is not the case    with the comparatives 5 and 6, and also gives very good melt flow    index results, which is not the case with comparative 3.    A synergy effect is therefore found between the protagonists of the    AM939/Lotryl/AX8900 trio of the impact modifier according to the    invention making it possible to achieve an appreciable compromise    between impact strength and melt flow of the thermoplastic polyester    compositions according to the invention.    -   The examples below were produced with PET/impact modifier        compositions such as those defined in % by weight in TABLE 10.        This table also give other values such as the MFI of the        compositions appearing therein and their impact strength by        measuring the notched Charpy impact behaviour according to the        standard defined above at various temperatures T (T=20° C.,        0° C. and −30° C.).        The examples below were made with the following products:

-   PET: polyethylene terephthalate having an MFI of 40–50 (275° C./2.16    kg) sold under the brand name ESTAPAK®9921 by Eastman;

-   AX8900: composition defined above;

-   E920: composition defined above;

-   AM939: composition defined above;

-   Lotryl: ethylene-butyl acrylate copolymer comprising 30% by weight    of acrylate and having an MFI of 2 (190° C./2.16 kg).    In view of the MFI and impact strength results reported in TABLE 10,    it may be seen that the compositions comprising only AX8900    (comparatives 1) and only the duo Lotryl/AX8900 (comparative 4) as    impact modifier offer good impact strength to the detriment of melt    flow index, which is mediocre. Furthermore, it is found by studying    the results of the compositions comprising only a core-shell (AM939    in the case of comparative 2 or E920 in the case of comparative 3)    as impact modifier that these compositions offer a poor impact    strength but a better melt viscosity.    Analysis of our results obtained with compositions comprising the    impact modifier according to the invention clearly shows an    improvement in the viscosity over comparatives 1 and 4 together with    an improvement in the impact strength over comparatives 2 and 3.    Our results indubitably demonstrate that our impact modifier is    superior to the comparative impact modifiers and sheds light on the    synergistic effect of the CS/Lotryl/AX8900 compounds, forming an    impact modifier according to the invention, on the melt flow index    and the impact strength of our thermoplastic polyester compositions.

Although the invention has been described in conjunction with specificembodiments, it is evident that many alternatives and variations will beapparent to those skilled in the art in light of the foregoingdescription. Accordingly, the invention is intended to embrace all ofthe alternatives and variations that fall within the spirit and scope ofthe appended claims. The foregoing references are hereby incorporated byreference.

TABLE 9 AM939/ Impact strength (foot.pound/inch) PBT AM939 Lotryl AX8900Lotryl/AX8900 MFI (g/10 min) T = 20° C. T = −20° C. T = −30° C. T = −40°C. 100%   0%  0%  0% 0/0/0 PBT Base 37.9 1–2 — — — 80%  0%  0% 20%0/0/100 Comparative 1 6.7 17.6 2.9 — — 75% 25%  0%  0% 100/0/0Comparative 2 14.6 3.1 — — — 75% 12.5%    0% 12.5%   50/0/50 Comparative3 0.6 25 23 23 18 75%  0% 25%  0% 0/100/0 Comparative 4 38.4 1.3 — — —75%  0% 12.5%   12.5%   0/50/50 Comparative 5 11.7 15.1 2.6 — — 75%12.5%   12.5%    0% 50/50/0 Comparative 6 18.7 4.4 — — — 75% 7.5% 12.5%    5% 30/50/20 7.2 75% 7.5%  7.5%  10% 30/30/40 4.4 75% 7.5%   5%12.5%   30/20/50 4.6 75% 12.5%   7.5%   5% 50/30/20 5.5 20 18 14.5 3 75%12.5%   6.25%   6.25%   50/25/25 4.1 21.5 17.5 4 75% 12.5%    5% 7.5% 50/20/30 3.4 18.5 19 4 75% 15%  5%  5% 60/20/20 4.7 75% 15%  3%  7%60/12/28 3.2 22.5 18.5 3.5 75% 17.5%   4.5%   3% 70/18/12 9.1 80%10.0%   4.0%  6.0%  50/20/30 5.7 22.5 17.5 6 80% 10.0%   5.0%  5.0% 50/25/25 4.9 22 17 3 80% 10.0%   6.0%  4.0%  50/30/20 6.2 21 14.5 3 70%15.0%   6.0%  9.0%  50/20/30 2.8 21 23 9 70% 15.0%   7.5%  7.5% 50/25/25 3.3 20.5 21 7 70% 15.0%   9.0%  6.0%  50/30/20 3.7 19.5 18 6.5

TABLE 10 Impact strength (kJ/m²) PET AM939 E920 Lotryl AX8900AM939/Lotryl/AX8900 MFI (g/10 min) T = 20° C. T = 0° C. T = −30° C.100%  PET Base 40–50 3.2 3.2 3.2 80% 20% Comparative 1 1.8 22 15 7 80%20% Comparative 2 7 8 7.3 4.7 80% 20% Comparative 3 9 5.4 4.7 3 80% 17% 3% Comparative 4 1.6 19.9 15.1 9.5 80%  6% 11%  3% 28.6/57.1/14.3 5 to6 12.6 10.7 7.2 80%  9%  9%  3% 42.9/42.9/14.3 7 to 8 12 10.8 6.7 80% 9%  9%  3% 42.9/42.9/14.3 2 12.7 11.3 7.6 80% 11%  6%  3%57.1/28.6/14.3 2 to 3 10.1 8.1 5.3 80% 11%  6%  3% 57.1/28.6/14.3 6 10.59.3 5.8

1. Thermoplastic polyester compositions free of polycarbonate,comprising, by weight, the total being 100%: 60 to 99% of athermoplastic polyester; 1 to 40% of an impact modifier comprising: (a)a core-shell copolymer (A); (b) an ethylene copolymer (B) comprisingethylene, an unsaturated carboxylic acid anhydride and an ester of anunsaturated carboxylic acid (B1); and (c) a copolymer (C) selected fromcopolymers consisting of ethylene and alkyl(meth)arcylate (C1),optionally neutralized copolymers consisting of ethylene and(meth)acrylic acid (C2) and blends thereof.
 2. Compositions according toclaim 1, wherein the polyester is PET or PBT and mixtures thereof. 3.Compositions according to claim 1, comprising from 0 to 500 parts byweight of copolyetherester per 100 parts of thermoplastic polyester. 4.Compositions according to claim 1, wherein the copolymer (A) comprisesan elastomer core, advantageously an n-octyl acrylate core, and at leastone thermoplastic shell, advantageously a methyl methacrylate shell. 5.Compositions according to claim 1, wherein the copolymers (B1) areethylene-alkyl (meth)acrylate-maleic anhydride copolymers which comprisefrom 0.2 to 10% by weight of maleic anhydride and from 5 to 40% byweight of alkyl (meth)acrylate.
 6. Compositions according to claim 1,comprising, per 100 parts by weight, 65 to 95 parts and 35 to 5 parts ofpolyester and of impact modifier, respectively.
 7. Compositionsaccording to claim 1, wherein the proportions by weight of (A), (B) and(C) are 15 to 80, 5 to 60 and 5 to 80%, respectively, and(A)+(B)+(C)=100%.
 8. Compositions according to claim 7, wherein theproportions by weight of (A), (B) and (C) are 20 to 35, 40 to 60 and 10to 40%, respectively, and (A)+(B)+(C)=100%.
 9. Compositions according toclaim 7, wherein the proportions by weight of (A), (B) and (C) are 25 to35, 5 to 10 and 60 to 70%, respectively, and (A)+(B)+(C)=100%. 10.Compositions according to claim 7, wherein the proportions by weight of(A), (B) and (C) are 40 to 75, 10 to 35 and 10 to 35%, respectively, and(A)+(B)+(C)=100%.
 11. Compositions according to claim 5, wherein theamount of alkyl (meth)acrylate is from 5 to 40%.
 12. Thermoplasticpolyester compositions comprising, by weight, the total being 100%: 60to 99% of a thermoplastic polyester; 1 to 40% of an impact modifiercomprising: (a) a core-shell copolymer (A); (b) an ethylene copolymer(B) comprising ethylene, an unsaturated carboxylic acid anhydride and anester of an unsaturated carboxylic acid (B1); and (c) a copolymer (C)selected from copolymers consisting of ethylene and alkyl(meth)acrylate(C1), optionally neutralized copolymers consisting of ethylene and(meth)acrylic acid ethylene (C2) and blends thereof, wherein theproportions by weight of (A), (B) and (C) are 15 to 80, 5 to 60 and 5 to80%, respectively, and (A)+(B)+(C)=100%.
 13. Compositions according toclaim 12, comprising from 0 to 300 parts by weight of polycarbonate per100 parts of thermoplastic polyester.
 14. Polyethylene terephthalatecompositions free of polycarbonate, comprising, by weight, the totalbeing 100%: 60 to 99% of polyethylene terephthalate; 1 to 40% of animpact modifier comprising: (a) a core-shell copolymer (A); (b) anethylene copolymer (B) comprising ethylene, an unsaturated carboxylicacid anhydride and an ester of an unsaturated carboxylic acid (B1),ethylene-unsaturated epoxide copolymers (B2) and blends thereof; and (c)a copolymer (C) selected from copolymers consisting of ethylene andalkyl(meth)acrylate (C1), copolymers consisting of ethylene and(meth)acrylic acid (C2) and blends thereof.
 15. Compositions accordingto claim 14, wherein the ethylene-unsaturated epoxide copolymers (B2)are ethylene-alkyl (meth)acrylate-unsaturated epoxide copolymersobtained by copolymerization of the monomers and contain from 0 to 40%by weight of alkyl (meth)acrylate and up to 10% by weight of unsaturatedepoxide.